In an X-ray CT apparatus, a rotary anode type X-ray tube is used in order to minimize a thermal influence on an X-ray tube anode due to irradiation with X-rays. The rotary anode type X-ray tube is configured to include a stator coil disposed outside the tube, and a rotary anode disposed inside the tube. The stator coil is connected to a starter circuit. The starter circuit supplies a three-phase AC voltage or a voltage shifted by 90 degrees from a phase thereof, to the stator coil so as to generate a rotating magnetic field, thereby rotating the anode inside the tube. When the voltage starts to be supplied to the stator coil from the starter circuit, a rotation speed of the anode does not reach a predetermined rotation speed, and thus X-rays are applied after a predefined waiting time period elapses. The waiting time period is a time period required for the rotation speed of the anode to be increased to the predetermined rotation speed or higher, and is a fixed time period obtained in advance. Consequently, electron beams are prevented from being applied to a cathode from the anode before the predetermined rotation speed is reached.
On the other hand, PTL 1 discloses an X-ray apparatus which performs control of a rotation speed of an anode as follows. If an operator selects an X-ray tube device and inputs scanning conditions thereto, and a starter device obtains a model of the X-ray tube device and reads a rating corresponding to the model of the X-ray tube device from means for storing a relationship between a rotation speed and a rating of the rotary anode for each model of an X-ray tube device. Next, a retention rotation speed during scanning of the rotary anode of the X-ray tube device is calculated on the basis of the set scanning condition, and a rotation speed of the rotary anode of the X-ray tube device is increased to the calculated retention rotation speed during scanning and is then maintained. The starter device is provided with a rotation speed detector, and completion of a scanning preparation operation is displayed if a detected rotation speed is increased to the retention rotation speed during scanning. Consequently, since a rotation speed is not required to be increased to a high rotation speed in the same way and can thus be increased to the retention rotation speed during scanning corresponding to the scanning condition, it is possible to reduce an activation time.